After years of service, the power strips in my equipment racks are getting
tired. Some of the outlets are dead or intermittent, causing occasional
clicks and pops. Yeah, I bought the cheapest things available. Iíve never
felt the urge to spend money on surge and spike protectors, the only real
path to power conditioning IMHO (in my humble opinion) is an un-interruptible
power supply (UPS), which I donít have, yet!

I found the ultimate replacement while thumbing through the Hosfelt
Electronics surplus catalog (800-264-6464). They carry several models of
SL Waber Trimline-Series outlet strips. Part # UL7415-6 is a particular
favorite. At four feet long, it features fifteen snug-fitting grounded
outlets on 2-7/8 inch centers. Thatís right, thereís enough space to plug
in a wall-wart without sacrificing a neighboring outlet. Photo One shows
a road-ready wart secured to the strip with a tie-wrap. The quality is
infinitely better than the typical ten- or fifteen-dollar strip and, at
$58.95, is only slightly more expensive.

Photo One: Waber Power Strip has room for Wall-Warts

Trying to minimize power-related noises in a recording
environment can be a major challenge. No matter how much you try ó with
hospital-grade outlets, separate ground wires, a spike in the ground or
whatever ó sometimes itís NOT your lack of skill, finances or preparation.
It may be the gear that's at fault. Click
here for an example, or...

If your audio gear can detect subtle changes in
neighborhood power consumption, consider hiring your system out to the
FBI!Nobody likes noise, especially
when you're trying to be creative. Eliminating hum and buzz is not Voodoo.
It is about taking a systematic approach to troubleshooting. So,
in your spare time, put down that creative hat and try this new gee kmodel
on for size.

WHY POWER RELATED NOISES VARY

Copyright 1994 by Eddie Ciletti

Figure One: What "the juice" should look
like when it comes from the outlet.

Power at the outlet is supposed
to be pure hum, or more precisely, a sixty-hertz sine wave. Buzzes are
the harmonic contribution of power-hungry appliances such as air conditioners,
electric heaters, computers and light dimmers. Any device that can make
your lights dim when powered also creates spikes and mangles the waveform.
These are distortions that can be reflected back into the power line. Susceptible
gear will receive these "transmissions" either directly through the power
cable or radiated into the air.

Electric guitar pickups, for
example, are susceptible to all sorts of radiated noises, a fact not lost
on guitarists who intuitively position their axes for minimum noise. (Hopefully
they can still face the audience!) By wiring two standard pickups out-of-phase,
most of the noise will cancel. This is the principle behind the humbucking
pickup; two coils wired back-to-back into one assembly. Only one set of
coils faces the strings, so the music comes through relatively unscathed.
Some dynamic mics also include a humbucking coil.

Itís not so easy with audio gear. As your system grows,
so too does its susceptibility to power related noises. Specifically, gear
can be grounded by an audio cable, the third prong of the power plug, contact
with the rack rail and via computer interfaces such as the SCSI port. Each
additional connection causes a ground loop that can bring out the demons
in certain pieces of gear.

Power ( in the US ), as distributed to a standard wall
outlet as 120-volts, is "un-balanced." Hopefully the illustrtation
above will illuminate and not confuse. As shown, the smaller flat
socket on the "top" of the standard power outlet is, in electricianís jargon,
"hot." The electrical code designates that this wire will be BLACK,
though for the purpose of creating a mental picture the connection is RED
(as in "hot).

The larger, lower flat socket is connected to a
white wire called "neutral." (Depicted as blue as in, "cool.")
This is the return-to-earth connection, but (as shown in the tug-of-war
illustration below) high current demand can raise it from zero to a few
volts above ground. In doing so, it becomes contaminated with the
harmonic backwash from every electrical device on the line. This one of
the reasons un-balanced power has no inherent noise imunity, ESPECIALLY
if the equipment design has been compromised during production by cost-
and labor-saving steps.

Though it can be effective at reducing hum and buzz, but
not noise such as "hiss," many view Balanced Power as a Magic Cure-All,
which it is not.

Balanced power will reduce the hum IF you plug all your gear
into it, so, the transformer has got to be of significant power handling
capability.

Balanced power will not regulate your juice, for that, you
want a UPS ( which also has to be of significant power handling capability).
A UPS is better at both regulation AND eliminating power spikes than any
other product.

Balanced power will not fix what's bad about gear that is
sensitive to hums and buzzes (and other stuff you don't realize).
Gear (and wiring) that take advantage of balanced audio will inherently
have better imaging and transient response.

There is no magic about having gear that can pass audio and
ignore noise.

A BRIEF DIVERSION...

In the typical home, youíll find a single phase of 220
volts in the breaker box. This power is reserved for large air conditioning
systems or electric ranges. From each phase-to-neutral is 120 volts, the
sauce that feeds standard appliance outlets. The electricianís goal is
to balance the loads on each phase. The analogy is tug-of-war, where you
get to be the rope, A.K.A. Neutral. Both the "A" and "B" phases are
pulling, but so long as the load of each phase is equal, you (Neutral)
stay put.

When the load becomes unbalanced your system is likely
to pick up bizarre intermittent noises. This is especially true when more
than one outlet source is used. When possible, avoid potential problems
by plugging everything into one dedicated outlet. Before doing so, determine
the total power consumption in either of two ways: One: read the
specs either in the documentation or on the rear panel of the unit. Unfortunately,
adding up power specs may be difficult because power consumption can be
specified as Watta, Amps and VA (Volt-Amperes). Two: use an "Amprobe"
clip-on ammeter to measure the current being drawn. Be sure to add a 30%
to 50% safety margin. For example, if the total load is 10 amps, the typical
15 amp breaker will be happy. (Running too close to maximum will make the
breaker run hot or it may blow if everything is powered up at once.)

FORMULA RELATIONSHIPS

Fuses and circuit breakers are always specified in amperes
(AKA "amps"). The information on the back of the unit or in the operatorís
manual will be specified in watts (W) or volt-amperes (VA). The Power Formula
is: Power = Volts times Amps ( P = V I ). Since "I"
is the current in Amperes, "VA" is volt-amperes, which should be the same
as Watts except that the "power vector" must be considered (this detail
is not yet fully developed on this page). Since the current is "alternating"
and not "direct," we can not simply multiply volts and amps to get watts.
Expect to make a few phone calls to the manufacturer.

Meanwhile, here are a few tips to keep the beasts at bay.

Connect all of the gear into power strips, but

Donít daisy chain any power strips, yet.

Count all of the strips, then

Determine how many strips it will take to accommodate them.

Now, think like a tree...

Each piece of gear is a leaf...

Each branch is power strip...

All strips feed the trunk...

Which is like the main outlet, OK?

Some trees have two trunks...

It could happen!

If so, make sure both breakers are on the same power phase.

ISOLATED GROUND and BALANCED POWER

Is it worth the added expense?

Consider the following

An Isolated Ground (IG) can be worth the added expense, but ONLY when
approached in a very specific and consistent way. Otherwise the benefits
will be nominal at best. Almost all new systems are sonically clean,
so don't kid yourself into thinking you got what you paid for (IG) or got
away with not paying for (IG).

Assuming a New Installation

If everything is connected to the same noise source there will be no
noise. The problem with most systems is that, over time, connections
become loose. Inconsistent noises are the result of changes in temperature,
moisture and current demand over TIME.

FOR EXAMPLE

It is also important to consider the habit of electricians. Most
do house and commercial wiring, few have the sensitivity to do audio installtions.
It is quite common, for example, for outlet boxes to be run in series RATHER
THAN running a fresh wire back to the breaker box. Consider strings of
"holiday" lights where, if one bulb is pulled, the others go out.

In power distribution, daisy-chaining outlet boxes puts a potential
noise-maker at every juntion: hot, neutral and ground. Again, the tightness
of each connection is important, because the lack of same generates heat,
causing expansion (and contraction), which, over time, generates intermittent
noises into the system wiring. Power hungry appliances and audio gear could
potentially heat up every weak junction.

An Isolated Ground system requires the following:

1.) three wires: hot, neutral and insulated ground to the IG outlet.

PLUS

2.) To be legal, a metal jacketed cable securely connected to a metal
outlet box (if used). When metal studs and metal boxes are used,
there will be multiple ground connections. The isolated and INSULATED
ground wire can not be used for, nor can it touch, the metal box or metal
stud.

HOWEVER

Using the spike-in-the-ground approach, there is still the problem tht
results when all of the wires are in the same jacket. Consider that
even audio gear generates noise. The proximity of the ground wire
-- isolated or not -- to the hot and neutral means that gear noise will
be induced from the power lines into the ground wire.

To legally take full advantage of an true IG system, balanced power
distribution (BPD) is required. Yet another expense, BPD requires a power
transformer with 120 volt windings, precision center-tapped at the mid-point
to yield 60 volts (60-0-60) to both the former NEUTRAL and the somewhat
less HOT. With balanced power, minimal, if any. noise will be generated
into the ground wire, isolated or not.

IG sans BPD

To keep the ground wire clean, it should be run away from -- and not
parallel to -- the power lines. This is not "to code," but for the
moment, consider this:

In additon to the legal requirement of the standard hot-neutral-ground
cable to the outlet box, run a separate ground wire -- that is not paralllel
to any of the power lines -- to the isolated-ground outlets. ALL
of the ground wires -- legal and clean -- will go back to the same ground
bar in the breaker box. Assuming the same clean, tight connection
for every wire, the system should remain clean.

NOISE will occur if you join a clean system to a noisy system as might
occur when connecting to a guitar or bas amp via direct box. Of course,
ALL potential audio outlets should have their own ground wire and a straight
return to the breaker box.

Glossary of terms

Hertz (abbreviated Hz) is the frequency,
in cycles per second, of an alternating current (AC). When specifying voltage,
the RMS (root mean square) value is used so that the effective power is
equivalent to that of direct current (DC). For example, the voltage at
the power outlet is 120 volts RMS which is actually about 340 volts peak-to-peak.